Spring

Springs are interesting elements in physics, mainly because they behave differently than rigid bodies.

The spring force is a restorative force, in the direction counter to the deformation, defined by Hooke’s law:

$$F=k\Delta x$$

Similarly to capacitors, for springs in parallel:

$$k_{eq}=\Sigma k_i$$

And for springs in series:

$$\frac{1}{k_{eq}}=\frac{1}{k_1}+\frac{1}{k_2}+\dots$$